Boiler short cycles, turning on and off frequently with very short run times.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Short cycling mainly affects efficiency and wear, not immediate safety, but any combustion adjustments must be done by a professional.
- Observe cycle pattern: Note how long the Laars boiler runs before shutting off and how quickly it restarts.
- Check thermostat placement: Ensure the thermostat is not near heat sources or drafts that cause rapid temperature swings.
- Adjust boiler differential (if accessible): Some Laars controls allow increasing the temperature differential or anti-cycling time. Consult the manual and make small adjustments.
- Verify flow and zones: Ensure enough zones are open when the boiler fires; very small active loads can cause short cycling.
When to call a professional: Persistent short cycling may require system redesign (buffer tank, control changes) evaluated by a heating professional.